Method of providing an imprinted security feature

Abstract

Disclosed is a method of forming a security document including the steps of: providing a base layer having a top side; providing a color image onto an image area of the top side by printing colored ink, on the top. A lens structure is applied over the colored ink, the lens structure having a predetermined focal plane situated at a distance from the top side, and laser engraving a black image in through the lens structure and through the colored ink to form blackened image elements substantially at or near the focal plane.

The invention claimed is: 
     
       1. Method of forming a security document ( 1 ) comprising the steps of:
 providing a base layer ( 2 ) having a top side ( 6 ), 
 providing an image ( 3 ) having color image elements ( 3 ′, 3 ″, 3 ′″) onto an image area (Ai) of the top side ( 6 ) 
 providing a protective layer ( 4 ) over the image area (Ai) in a soft or liquid state, 
 imprinting a pattern ( 5 , 27 ) into the protective layer ( 4 ) in the image area (Ai) while in its soft or liquid state by contacting the protective layer ( 4 ) with an imprint member ( 16 , 20 ) that is provided with the pattern, and 
 hardening of the protective layer by irradiating it with optical radiation, 
 wherein, 
 the pattern ( 5 ) comprises an optical structure having dimensions smaller than 100 μm, wherein the imprint member ( 16 , 20 ) is transparent and flexible and the protective layer ( 4 ) is hardened by the transmission of the optical radiation through the transparent imprint member while it is contacting the protective layer, the imprint member ( 16 , 20 ) being removed from the protective layer ( 4 ) after at least partial hardening of the protective layer, followed by the step of providing a blackened pattern ( 7 ) into the base layer ( 2 ) by focusing a laser beam via the optical structure and laser engraving image elements into the base layer in a focal plane ( 8 ) that is situated at a vertical distance h of between 50 μm and 150 μm from the color image elements. 
 
     
     
       2. Method according to  claim 1 , wherein the image ( 3 ) is provided in the image area (Ai) via printing of transparent color image elements ( 3 ′, 3 ″, 3 ′″), the optical structure comprising an array ( 27 ) of lenticular lenses, wherein the blackened pattern ( 7 ) is provided in the base layer by the laser beam through the lenticular lenses and through the transparent color image elements ( 3 ′, 3 ″, 3 ′″). 
     
     
       3. Method according to  claim 2 , wherein the color image elements ( 3 ′- 3 ′″) have an average transmission of at least 50% in the wavelength range between 400 nm and 700 nm. 
     
     
       4. Method according to  claim 3 , wherein the color image elements ( 3 ′- 3 ′″) have a transmission of at least 50% at the wavelength of the laser beam. 
     
     
       5. Method according to  claim 1 , wherein the color elements ( 3 ′- 3 ′″) are contiguous or overlapping. 
     
     
       6. Method according to  claim 1 , wherein after removal of the imprint member ( 16 ,  20 ), the base layer ( 2 ) is transported to a personalization station ( 25 ) comprising the laser ( 29 ,  40 ), where after personalization data is provided into the base layer via the optical structure. 
     
     
       7. Method according to  claim 1 , a print controller ( 34 ) having a memory ( 33 ) being connected to an image applicator ( 35 ), the image being formed by storing image data in the controller memory ( 33 ) and providing an ink layer onto the base layer ( 2 ) via the image applicator that is connected to the controller, followed by scanning the laser beam ( 29 , 40 ) that is connected to a laser controller ( 38 ), over the image area (Ai), the laser controller ( 38 ) obtaining image data from the controller memory ( 33 ) for burning image elements into the base layer ( 2 ) through the array of lenses. 
     
     
       8. Method according to  claim 1 , wherein the protective layer is of larger dimensions than the image area. 
     
     
       9. Method of forming a security document ( 1 ) comprising the steps of:
 providing a plastics substrate ( 30 ) having an optical pattern ( 31 ), transporting the substrate ( 30 ) to a personalization site, 
 providing image data of a portrait ( 32 ) into a memory ( 33 ) of a print controller ( 34 ), the print controller being connected to an image applicator ( 35 ), 
 forming an image by providing an ink layer of color image elements onto the substrate ( 30 ) in an image area (Ai) via the image applicator that is connected to the print controller, 
 applying a protective layer ( 4 ) over the substrate ( 30 ) in a liquid or softened state, 
 imprinting a lens pattern ( 5 , 27 ) into the protective layer ( 4 ) overlying the image in the image area (Ai) while in its liquid or softened state by contacting the protective layer with a transparent and flexible imprint member ( 16 , 20 ) that is provided with the pattern, 
 hardening of the protective layer by the transmission of the optical radiation through the transparent imprint member ( 16 , 20 ) while it is contacting the protective layer( 4 ), 
 removing the imprint member ( 16 , 20 ) from the protective layer after hardening of the protective layer, 
 providing a laser controller ( 38 ) and a laser ( 40 ) connected to the laser controller, 
 providing image data of the portrait to the laser controller ( 40 ), and 
 scanning the laser beam across the lens structure by the laser controller and providing blackened image elements ( 26 ) based on the image data into the substrate ( 30 ) below the lens elements through the printed color image elements ( 3 ′- 3 ′″) into an underlying layer in a focal plane ( 8 ) that is situated at a vertical distance h of between 50 μm and 150 μm from the color image elements. 
 
     
     
       10. Method according to  claim 9  wherein the color image elements of ink have an average transmission of at least 50% in the wavelength range between 400 nm and 700 nm. 
     
     
       11. Method according to  claim 10 , wherein the color image elements ( 3 ′- 3 ″′) of ink have a transmission of at least 50% at the wavelength of the laser beam. 
     
     
       12. Method of forming a security document ( 1 ) comprising the steps of:
 providing a base layer ( 2 ) having a top side ( 6 ), 
 providing a color image ( 3 ) onto an image area (Ai) of the top side ( 6 ) by printing color image elements ( 3 ′- 3 ′″) of ink having an average transmission of at least 50% in the wavelength range between 400 nm and 700 nm, on the top side ( 6 ), 
 wherein, 
 a lens structure is applied over the colored ink, the lens structure having a predetermined focal plane ( 8 ) situated at a distance from the top side ( 6 ), and 
 laser engraving blackened image elements ( 7 ) through the lens structure and through the color image elements ( 3 ′- 3 ′″) to form the blackened image elements substantially at or near the focal plane. 
 
     
     
       13. Method according to  claim 12 , wherein the focal plane ( 8 ) that is situated at a vertical distance h of between 50 μm and 150 μm from the color image elements. 
     
     
       14. Method according to  claim 12 , wherein the color image elements have a transmission of at least 50% at the wavelength of the laser beam. 
     
     
       15. The method of  claim 2 , wherein the transparent color image elements ( 3 ′, 3 ″, 3 ′″), are Yellow, Magenta and Cyan. 
     
     
       16. The method of  claim 4 , wherein the color image elements ( 3 ′- 3 ′″) have a transmission of at least 80% at the wavelength of the laser beam. 
     
     
       17. The method of  claim 8 , wherein the protective layer covers substantially the entire base layer ( 2 ). 
     
     
       18. The method of  claim 11 , wherein the color image elements ( 3 ′- 3 ″′) of ink have a transmission of at least 80% at the wavelength of the laser beam. 
     
     
       19. The method of  claim 14 , wherein the color image elements have a transmission of at least 80% at the wavelength of the laser beam. 
     
     
       20. Method according to  claim 2 , wherein the color elements ( 3 ′- 3 ′″) are contiguous or overlapping.